It is a blue over red horizontal bicolour with a white
rectangle in the centre, containing the coat of arms. It is
denoted as a war-flag. The flag is depicted in the ALBUM on p.16,
image no.314. According to Flaggenbuch its ratio is
17:27(measured by myself).
The flag must have been used in the 1930' and perhaps also in the
1920'.
Within the coat of arms one can clearly recognize a coastal line
behind the sea and the sunk ships on both sides having two masts
with white flags.Sources: Flaggenbuch; edited by HQ of German navy;
Berlin 1939, reprinted Zwickau 1992; p.78 Welt, Cigarette ALBUM
"Die Welt in Bildern Album 7 : Flaggen der aussereurpäische
Staaten", edited between 1928 and 1932 according to the
international Schneider, boundaries in the included map of the
world. Klaus-Michael Schneider, 29 October 2007

Here is the flag or "ensign" of the Haitian Coast
Guard.
The legend reads: "République d'Ha´ti" and
"Toujours Pręts" (which, like the USCG motto
"Semper Paratus", means "always ready").Source: Flags of the World (Gresham and Carr, 1961)Miles Li, 12 August 2008

I suppose that like the US Coast Guard
"ensign", the flag is actually not used as a
national ensign on ships, but rather as an additional flag
hoisted on the ship 8and also used on land on their premises and
in offices).
Is this still used today?Željko Heimer, 12 August 2008

It seems that it is not in use I find a photo
in which a flag is
painted on the wall of Haitian Coast Guard Station
Port-au-Prince. I don't know it it is the national flag or the
national colors with the emblem of the "Garda Cote".
There is a flag on the boats but I think that it is the Naval Ensign.Dov Gitterman, 12 August 2008

It is a plain blue flag with a white rectangle in its centre.
The flag is depicted in the ALBUM on p.16, image no.316.
Flaggenbuch implicitely denies the existence of a special pilot
flag, saying on p.78, that the pilot used the trade flag, a
simple blue over red horizontal bicolour. If a special pilot flag
had existed, it must have been used before 1939.
Sources: Flaggenbuch; edited by HQ of German navy; Berlin 1939,
reprinted Zwickau 1992; p.78 Cigarette ALBUM "Die Welt in
Bildern Album 7 : Flaggen der Welt, aussereurpäische
Staaten", edited between 1928 and 1932 according to the
international boundaries in the included map of the world.Klaus-Michael Schneider, 29 October 2007